Our objective is to study structural and functional properties of acetylcholinesterase (AChE) and to investigate its interaction with and role in excitable membranes. Several forms of AChE from electric organs of the electric eel that are characterized by various sedimentation coefficients have been isolated by affinity chromatography in our laboratory. Structural distinctions between these forms have been studied by polyacrylamide gel electrophoresis in sodium dodecylsulfate and by amino acid analysis, and we have identified collagen-like subunits in 185 and 14S AChE forms which are linked by disulfide bonds to catalytic subunits. We propose to isolate and characterize these collagen-like subunits to prepare antibodies to them, and to investigate the hypothesis that they mediate an association with the basement membrane. This investigation will focus on the purification of AChE-rich membranes by affinity chromatography.